Theresa May was facing fresh Brexit pressure on a number of fronts after a surprise ministerial resignation left Tory wounds on EU withdrawal exposed again.

Jo Johnson’s decision to quit as transport minister saw pro-EU and arch-Brexiteers in the Conservative Party unite to attack the Prime Minister’s stance.

Mrs May also had to deal with a challenge from Northern Ireland’s DUP whose support she needs to command a Commons majority.

Mr Johnson’s dramatic move to exit Government, four months after his brother Boris dealt Mrs May a political blow by walking out of Cabinet, took Westminster by surprise.

However, his call for a new Brexit referendum was attacked by Mrs May’s supporters.

Children and Families Minister Nadhim Zahawi cautioned against a new poll, telling the BBC such a move would “unleash forces that no politician… would actually know where it would end up”.

Jo Johnson was transport minister before his resignation (Stefan Rousseau/PA)

He added: “In the sense that if you betray the British people where they no longer believe in democracy… you don’t know what the consequences are.”

Amid the Tory infighting, DUP leader Arlene Foster made it clear her party would vote against the PM’s current proposals.

The DUP leader said “no unionist” could back Mrs May’s apparent advocacy of a withdrawal treaty that includes a Northern Ireland specific backstop measure to avoid a hard border on the island of Ireland.

Stormont’s former first minister insisted there were “many others” in the Conservative Party who could also not support the Prime Minister’s proposals.

Ahead of a conference of the Eurosceptic Bruges Group on Saturday, Tory MP Mark Francois said further ministerial resignations could not be ruled out.

He told the BBC: “When we get the final deal, and it feels like that’s not very far away, Cabinet ministers will have to look into their hearts and see whether or not they feel they can support it.

“And, if they can’t, because they believe it’s a bad deal for the country, then, honourably, they would have to resign.”

Boundless admiration as ever for my brother Jo. We may not have agreed about brexit but we are united in dismay at the intellectually and politically indefensible of the UK position 1/2 https://t.co/QI4tMpLecc